In pending application Ser. No. 925,955, filed Oct. 3, 1986, there are disclosed 1-methyl-15.alpha.-alkylandrosta-1,4-diene-3 17-diones of the formula ##STR2## wherein R.sub.15 is alkyl of 1-4 carbon atoms, alkyl substituted in the 1, 2 or 1 and 2 positions by hydroxy, C.sub.2 -C.sub.7 -alkanoyloxy or 1,2-isopropylidenedioxy.
The compounds are used in the inhibition of estrogen biosynthesis. In addition, pending application Ser. No. 152,222, a CIP of Ser. No. 925,955, discloses estrogen inhibitors of the above formula wherein R.sub.15 is C.sub.2-10 -alkyl or C.sub.2-10 -alkyl substituted in the 1 and 2 position by two C.sub.1-7 -alkanoyloxy groups. The alkanoyloxy groups may be identical or different.